Illuminated display device

ABSTRACT

An illuminated display device ( 10 ) according to the present invention comprises an image sheet ( 48 ) comprising, in turn, a plurality of series of image portions ( 47   a   , 47   b   , 47   c ) etc. and a mask sheet ( 62 ) having alternative opaque strips ( 63 ) and transparent windows ( 61 ). The mask sheet ( 62 ) is located in face-to-face relation to the image sheet ( 48 ). First and second roller means ( 64, 66 ) are located in a substantially parallel spaced-apart arrangement relative to the image sheet ( 48 ) and the mask sheet ( 62 ) and are operatively associated with one of the image sheet ( 48 ) and the mask sheet ( 62 ). The device ( 10 ) is provided with means to oscillatingly move the one of the image sheet ( 48 ) and the mask sheet ( 62 ) relative to the other of the image sheet ( 48 ) and the mask sheet ( 62 ). The moving means comprises a drive means ( 84 ), a cam ( 88 ); a cam follower lever ( 90 ) or ( 91 ) associated with the cam ( 88 ); and a crank mechanism comprising a crank lever ( 92 ) or ( 94 ) operatively associated with the first roller means ( 64 ) and a linkage mechanism comprising the cam follower lever ( 90 ) or ( 91 ) and the crank lever ( 92 ) or ( 94 ).

The present invention relates to an illuminated display device fordisplaying an image from a series of image portions on an image sheet.The invention has particular application for, but is not limited to,“Point of Sale” or “Commercial Poster” advertising.

There are several means of advertising by illuminated display devices orcabinets, catering for a range of poster sizes. Most of such displaydevices display a single advert. The advert is usually printed on paperwhich is secured to the front of a diffuser platen and then backlit.

There are known illuminated display devices which illuminate an imagesheet, for example, an ink jet print or a photographic print, the imagesheet comprising two series of image portions in strip formstrategically placed behind, or in front of, a mask sheet, or grid, themask sheet having a series of transparent windows alternating with aseries of opaque strips, either the mask sheet or the image sheet beingmoved so that the two series of image portions on the image sheet arealigned, in turn, with the series of transparent windows on the masksheet, thereby permitting an image formed from one of the two series ofstrip images, to be visible.

It will be appreciated that the clarity of each of the images, thechangeover of the images and the dwell time on each of the images is ofparamount importance to the advertiser. This is determined by theprecision of both the assembly of the image sheet and the matching masksheet and the drive means and tensioning means used to move the imagesheet and the mask sheet relative to one another.

Previous designs, in both respects, have limited the dimensions ofilluminated display devices and have been associated with significantdrawbacks in terms of clarity of each of the visible images.

The present invention overcomes the limitations associated with knownilluminated display devices and achieves an illuminated display devicewithout the previous restrictions as to its dimensions and stabilityunder varying atmospheric conditions. This enables the illuminateddisplay device of the present invention to be used in all recognisedsizes thereby vastly increasing its potential customer base.

According to the invention there is provided an illuminated displaydevice comprising an illuminated image sheet, comprising a plurality ofseries of image portions; a mask sheet having alternate opaque andtransparent strips, the mask sheet being located in face-to-facerelation to the image sheet; first and second roller means in asubstantially parallel spaced-apart arrangement relative to the imagesheet and the mask sheet, the first and second roller means beingoperatively associated with one of the image sheet and the mask sheet;and means to oscillatingly move the one of the image sheet and the masksheet relative to the other of the image sheet and the mask sheet, themoving means including a drive means; a cam rotatably driven by thedrive means; a cam follower lever associated with the cam; and a crankmechanism comprising a crank lever operatively associated with the firstroller means and a linkage mechanism connecting the cam follower leverand the crank lever.

Preferably, the image sheet comprises at least three series of imageportions, preferably at least four series, most preferably five series.

The illuminated display device of the present invention is suitable forinterior and exterior displays. The illuminated display device of thepresent invention enables a number of images to be viewed in turn.Depending on whether the illuminated display device is for interior orexterior end use, the display device may be illuminated from differingangles, for example, back-illuminated, side-illuminated orfront-illuminated by, for example, sunlight or an external light source.

The visible image may comprise several separate images or,alternatively, several images creating a story line or, furtheralternatively, several images arranged to provide the perception ofanimated movement.

The display device of the present invention usually has three sections:a substantially rigid rear housing, which may contain a light source (ifback-illuminated), for installation, for example, on a display stand or,more usually, on a wall; a front housing having a protective screencover which optionally has a non-reflecting surface and which can alsocontain a light source (if front-illuminated); and a centre sectioncomprising an image sheet, a mask sheet or grid having at least oneseries of transparent windows alternating with a series of opaque strips(opaque in this context means substantially non-transparent), the masksheet being located in face to face relation to the image sheet; and themeans to move the image sheet and the mask sheet in relation to oneanother. If desired, the centre section can also contain a light sourcefor back-illumination.

Advantageously, two opposing cam follower levers and two opposing crankmechanisms are provided so that the drive means is arranged, inoperative association with the first and second roller means, to impartoscillating movement to the first roller means and equal and oppositeoscillating movement to the second roller means.

Preferably, the length of the first and second roller means is 10%-50%of the width of the image sheet.

More preferably, the one of the image sheet and the mask sheet which isoperatively associated with the first and second roller means istensioned by providing at least one pair of tension springs, the, oreach, pair of tension springs forming a substantially V-shapedarrangement of tension lines, the apex of the substantially V-shapedarrangement being the transverse mid-line of the opposite roller means;and an opposing at least one pair of tension springs forming asubstantially inverted V-shaped arrangement of tension lines, thesubstantially inverted V-shaped arrangement apex being the transversemid-line of the opposite roller means.

Advantageously, the image sheet and the mask sheet are supported on aplaten and the maximum height of curvature of the platen in the y-axisis between 0.3 and 2%, preferably 0.8%, of the length of the platen inthe y-axis.

More advantageously, the tension springs are arranged below a notionalextension of the y-axis curvature of the platen.

Even more advantageously, the platen has a maximum transverse curvatureof between 3% and 20% of the maximum longitudinal curvature of theplaten.

Preferably, each image portion forming one series of image portions hasa pitch of 0.025-0.25%, preferably 0.05-0.21%, most preferably0.075-0.15%, of the y-axis length of the image sheet.

More preferably, each transparent window of the mask sheet has a pitchof 30-60%, preferably about 45%, of the pitch of each image portion.

It will be appreciated that, as a consequence of the substantiallyparallel configuration of the first and second roller means relative tothe image sheet and the mask sheet, many advantages ensue.

Specifically, the substantially parallel configuration of first andsecond roller means permits wide variations in the dimensions of theimage sheet and the mask sheet, for example, within the range of A4, A3,A2, A1, A0 to six sheet dimensions. Table 1 shows the x-axis(transverse) and y-axis (longitudinal) dimensions of such sheets,although it will be appreciated that, when used in landscape format, thex-axis and y-axis dimensions are transposed. Equally, the illuminateddisplay device of the present invention can be used to displayintermediate sizes or larger sizes, depending on the desired endapplication. In addition, the illuminated display device of theinvention can accommodate additional combination dimensions, forexample, A0 wide (840 mm) and A4 high (235 mm).

TABLE 1 Sheet Transverse Longitudinal Identity (mm) (mm) A4 165 235 A3235 330 A2 420 595 A1 595 840 A0 840 1190 6 sheet 1200 1800

Provision of third and fourth roller means (not shown) at right anglesto the first and second roller means, with a second drive means (notshown) operatively associated with the third roller means and,preferably, with the fourth roller means, permits the display of aseries of images in either portrait or landscape configuration, asdesired.

It will be appreciated that the one of the mask sheet and the imagesheet which is oscillatingly moved under the influence of the movingmeans, is, in effect, an integral part of the moving means. Thisintegral role results in improved clarity of the displayed image.

Furthermore, the dimensional flexibility of the image sheet and the masksheet opens the way for further opportunities in the arrangement ofimages on the image sheet—previously only two or three series of imageportions in strip form have usually been used on a single image sheet.

Due to the improved moving means of the present invention, up to fivefull series of non-animated image portions in strip form can beincorporated on an image sheet for use in an illuminated display deviceof the invention. Equally, up to ten full series of animated imageportions in strip form can be incorporated on an image sheet. Inaddition, the image sheet can incorporate various series of imageportions arranged in a grid configuration, so that several images are ondisplay at the same time. Thus, up to five sequential images can bedisplayed in a grid configuration, each composed of several individualimages.

Embodiments of the invention will now be described, by way of example,with reference to the accompanying drawings, in which:

FIG. 1 is a perspective front view of an illuminated display deviceaccording to the invention, in which an image sheet and a mask sheethave been omitted for clarity and in which a platen is transparent;

FIG. 2 is a perspective front view of a tensioning means of theilluminated display device of FIG. 1;

FIG. 3 is an enlarged perspective partial view of the tensioning meansof FIG. 2;

FIG. 4 is a rear perspective view of the illuminated display device ofFIG. 1;

FIG. 5 is an enlarged view of a cam and opposed cam follower levers ofthe illuminated display device of FIG. 4;

FIG. 6 is an enlarged view of an alternative cam and opposed camfollower levers for use in the illuminated display device of FIGS. 1-4 ;and

FIG. 7 is an enlarged perspective partial view of a fixing means for usein the illuminated display device of FIGS. 1-4.

In the drawings, similar numerals have been used to indicate like parts.

Referring now to FIGS. 1-5 and 7 of the accompanying drawings, there isillustrated an illuminated display device according to the invention,generally indicated as 10.

The illuminated display device 10 of the invention comprises a rearhousing 12, a front housing 14, and a support means 16. The fronthousing 14 includes an opening 18 to permit the displayed image to beviewed therethrough.

In the illustrated embodiment, the support means 16 is provided with anillumination means comprising one or more light tubes 24. The lighttubes 24 may be provided with an electronic ballast ignition means 26although it will be appreciated that any ignition means will be suitablefor incorporation in the illuminated display device 10 of the presentinvention. The ignition means 26 is connected to a power supply (notshown) by a power cable (not shown).

The support means 16 also includes first and second oppositely disposedside walls 30, 32, which extend at right angles between third and fourthoppositely disposed side walls 34, 36. The outer margins of the firstand second side walls 30, 32 are substantially rectilinear and the outermargins of the third and fourth side walls 34, 36 each form asubstantially arcuate outwardly convex surface, hereinafter referred toas a curved support means, to support and shape a platen 38. The firstand second side walls 30, 32 are at the same height as the lower edges35 of the curved support means formed by each of the third and fourthside walls 34, 36. The height difference between the lower edges 35 andtransverse platen mid-line 37 is hereinafter referred to as the maximumy-axis curvature height.

The platen 38 has first and second substantially parallel rims 40′, 42′extending from first and second substantially parallel margins 40, 42,the margins 40, 42 being at right angles to third and fourthsubstantially parallel margins 44,46; and an arcuate outwardly convexsurface which curves outwardly from the margins 40, 42 partly becausethe platen 38 is supported on the curved support means. The first andsecond rims 40′, 42′ are attached by screws or the like fixing means tothe first and second side walls 30, 32, respectively, of the supportmeans 16. The platen 38 is usually opaque and, as such, may be formedfrom a plastics, for example, Perspex of Lexan (Trade Mark) or a glasstype material. Alternatively, the platen 38 may be substantiallytransparent and, in that event, the diffuser effect is created by theprinting method chosen for an image sheet 48. Specifically, the seriesof strip images may be photographed onto a diffuser support material.

The y-axis (longitudinal) curvature of the curved support means, andconsequently of the platen 38, is chosen at minimum radius to reducefriction between the image sheet 48 and the mask sheet 62, to maintainthe desired overall touching contact between the image sheet 48 and themask sheet 62, and to achieve optimum clarity of displayed image.Empirical experiments have indicated that the maximum y-axis curvatureheight of the curvature of the platen 38 relative to margins 40, 42should be between 0.3% and 2%, preferably 0.5 to 1.0%, most preferablyabout 0.8%, of the length of the platen 38 in the y-axis. Thus, themaximum y-axis curvature height of the platen 38 (at the platentransverse mid-line 38), and should, most preferably, be about 4.75 mmfor an A2 size portrait platen 38 and about 6.75 mm, 9.5 mm and 14.4 mmfor an A1, A0 and six sheet size portrait platen 38, respectively.

The curve of the arcuate convex surface of the platen 38 is selected toprovide sufficient tension between the image sheet 48 and a mask sheet62, so as to display the image without distortion but with minimalfriction between the image sheet 48 and the mask sheet 62. The radius ofthe curve can, for example, be up to 1 m on display devices for interiorapplications, and up to 4 m on display devices for larger interior, andexterior applications. The arcuate convex surface of the platen 38should be a constant curve so that constant contact between the imagesheet 48 and the mask sheet 62 is maintained. For larger displaydevices, it is necessary to support the platen 38 on pin struts 39 (seeFIG. 1) of the desired height, so as to maintain the desired constanty-axis (longitudinal) curve across the platen 38, which constantlongitudinal curve is generated, at lateral margins 44, 46, by the shapeof the curved support means and, thereby, prevent the occurrence ofindentations on the platen 38.

The curvature of the platen 38 and the desired touching contact betweenthe image sheet 48 and the mask sheet 62 is further enhanced byimparting a small transverse curvature (in the x-axis) between thecurved support means at each lateral margin 44, 46 of the unit 10. Thisis achieved by supporting the platen 38 on strategically positioned pinstruts 39 of a height to support and maintain a desired transversecurvature. The desired maximum transverse curvature (in the x-axis)should be a further between 3% and 20% of the maximum longitudinalcurvature (y-axis). For example, if the maximum height of thelongitudinal curvature is raised by 10 mm, then the maximum transversecurvature height should be further raised by between 0.3 and 2.0 mm andthus, at an intersection of the transverse and longitudinal platenmid-lines 37, 39, the platen 38 is between 10.3 and 12 mm higher thanthe height of the lower edges 35. It will be appreciated that the pinstruts 39 should, desirably, be translucent with as small as is possiblea diameter so as not to restrict illumination or cause dark marks orreflections on the illuminated image.

An image sheet 48 is located, in use, on the platen 38 and is fixed inposition on the platen 38 by a fixing means, generally indicated as 50(see FIG. 7). The fixing means 50 comprises a pair of forwardly disposedimage locating pins 52, one adjacent each lateral margin 44, 46 of theplaten 38, each of which is pivotably mounted at 53 on the respectiveside walls 34,36 forming the platen curved support means. Each pin 52extends through a slot 54 provided in the platen 38 and through apush-fit sized aperture 56 provided in the image sheet 48.

A slot 58 is provided in the rear housing 12 (see FIG. 7), through whichprotrudes a screw-threaded pin/nut/friction washer arrangement 60. Inuse, the image sheet 48 can be moved relative to the first and secondmargins 40, 42 of the platen 38 by pivotably urging the, or each, imagelocating pin in the desired direction and by subsequently tightening theor each nut/friction washer against the rear housing 12, when one seriesof strip portions on the image sheet 48 has been aligned, in the x-axis,with a series of transparent windows 61 on the mask sheet 62.

A mask sheet 62 is located, in use, on top of the image sheet 48/platen38. First and second roller means generally indicated as 64, 66,respectively, are arranged in a substantially parallel, spaced-apartconfiguration, with the main axes (longitudinal axes) of the first andsecond roller means 64, 66 substantially parallel with the respectivefirst and second side walls 30, 32 of the support means 16. Each rollermeans 64, 66 includes a respective short drive shaft 68 which isrotatably mounted on the support means 16 using a pair of rotationbearings (see FIG. 3). Each drive shaft 68 is rotatably supportedbetween the pair of rotation bearings 69. Each pair of rotation bearings69 is adjustable, back and forth, in the longitudinal direction of theroller means 64, 66. This has been found necessary to ensure optimaltensioning of the mask sheet 62 since the longitudinal mid-line 39 ofthe mask sheet 62 must be secured to the exact middle (transversemid-line) 65 of each roller means 64, 66, to avoid distortion of themask sheet 62.

The mask sheet 62 is provided with extensions 74, 74′ for reversibleengagement of the mask sheet 62 between respective substantiallyC-shaped members 70 (sleeves) and the drive shafts 68 of the first andsecond roller means 64, 66.

It is desired that the top circumference of the first and second rollermeans 64, 66 be positioned at, but not above, a notional extension 57 tothe y-axis curvature of the platen 38. The top circumference of thefirst and second roller means 64, 66 may be up to 2 mm lower than thenotional extension to the y-axis curvature of the platen 38. Thus, thesmallest distance between the first or second roller means 64, 66 andthe notional extension 57 is 0-2 mm.

The mask sheet 62 is secured to the roller means 64, 66 by means of thesubstantially C-shaped sleeve 70 and a screw 71 arrangement whichsecurely clamps the longitudinal mid-line 39 of the extensions 74, 74′of the mask sheet 62 to the transverse mid-line 65 of the first andsecond roller means 64, 66. This imparts oscillating movement to themask sheet 62 without any angular distortion of the mask sheet 62. Themask sheet 62 therefore becomes an integral part of a moving means 82.

Tensioning means, generally indicated as 78, in the form of a pluralityof equal and opposing tension springs 80, maintain the mask sheet 62 intouching contact with the image sheet 48. The tension springs 80 arelocated to hold the mask sheet 62 above, and in touching contact with,the image sheet 48, without distortion of the mask sheet 62. For an A2size device, the tension springs 80 are arranged in two opposed pairs,so that tension is conveyed across the mask sheet 62 to the transversemid-line 65 of the opposite roller means, as diagrammatically indicatedby tension lines 81 on FIG. 2. Thus, each tension spring 80 of a pairtensions the mask sheet 62 between respective adjacent laterally opposededges of the mask sheet 62 and the screw 71 at the transverse mid-line65 of the longitudinally opposite sleeve 70 thus forming a substantiallyV-shaped arrangement of tension lines 81.

The one pair is opposed by a second pair of tension springs, forming asubstantially inverted V-shaped arrangement of equal and opposingtension lines 81. However, for an A0 size device (see FIGS. 2 and 3),four pairs of regularly spaced opposed tension springs are required(forming two substantially V-shaped arrangements of tension lines 81 andtwo substantially inverted V-shaped arrangements of tension lines 81),whilst, for a six sheet size device (not shown), six pairs of regularlyspaced opposed tension springs are required. Each tension spring 80must, in any event, exert tension along a notional tension line 83between its point of engagement with the mask sheet 62 and thetransverse mid-point 65 of the opposite sleeve 70. In addition, theaction of each tension spring 80 must be balanced by an opposing tensionspring 80. Thus, the positioning of the tension springs 80 must besymmetrical about both the longitudinal mid-line 39 of the platen 38 andthe transverse mid-line 37 of the platen 38.

When the roller means 64, 66 oscillate the mask sheet 62, the springs 80compensate for (or dampen) the oscillating movement, while retainingtension and overall contact with the image sheet 48. The tension springs80 are positioned to pull at or below a notional extension 57 extendingfrom the y-axis curvature of the platen 38. The top circumference of thetension springs 80 may be positioned at or just below (but not above)the notional extension 57. Thus, the smallest distance between thetension springs 80 and the notional extension 57 is 0-2 mm. As the masksheet 62 oscillates, in the y-axis , each series of image portions isdisplayed for a predetermined time and then fades away as the nextseries of image portions becomes visible.

Alternative means of locating, securing and tensioning the mask sheet 62have been tried without success. For example, the second roller means64, 66 could be increased in length to equal the overall width of theplaten 38. In that event, the mask sheet 62 could be directly clamped tosuch long roller means or could be indirectly connected to the suchlonger roller means by regularly spaced springs, for example, on an A0size device, at five equally spaced points. There are two maindisadvantages with such systems.

Highly accurate tensioning of the mask sheet 62 to the drive rollers 64,66 is necessary to achieve correct tension of the mask sheet 62 so as toavoid distortion whilst maintaining touching contact with the imagesheet 48 across the length and breadth of the mask sheet 62.Additionally with such a system a small twist in the display unit,during for example installation on a wall, can put the longer driverollers out of exact parallel configuration with the platen 38 andresult in loss of touching contact between the image sheet 48 and themask sheet 62 with a resultant loss of image clarity.

The present method of tensioning the mask sheet overcomes thesedisadvantages by facilitating a lower accuracy level which toleratesinstallation accidents and the like.

Empirical experiments have found that a first and second roller means64, 66 having a length of 175 mm, may be used for A2 up to six sheetportrait size devices 10. Thus the first and second roller means 64, 66may be 10-50%, preferably 20-45%, of the width of the platen 38.

To change the image sheet 48, the image sheet 48 is disengaged from thepins 52 and the image sheet 48 is withdrawn by sliding it laterally inparallel to the rollers 64, 66 from below the mask sheet 62.

With particular reference to FIGS. 4-6 of the accompanying drawings, theilluminated display device 10 of the present invention includes a movingmeans generally indicated as 82. The moving means 82 includes a drivemeans or motor 84 having a drive shaft 86 extending therefrom. A cam 88(for non-animated use, usually a fixed velocity or constant rise,constant fall) is mounted on the drive shaft 86. Two opposing camfollower levers 90, 91 are provided to convert the rotary movement ofthe drive shaft 86 into fixed velocity oscillating movement of the camfollower levers 90, 91. It will be appreciated that the opposeddispositions of the cam follower levers 90, 91 ensures that theoscillating movement of the cam follower lever 90 is equal and oppositeto that of the cam follower lever 91.

In the preferred embodiment of the display device 10 of the invention(non-animated use), the lever mechanism carrying the cam follower leversis adjusted in leverage length relative to the spacing of the imageportions in strip form on the image sheet 48, to expose a pre-determinednumber of images in both the upward travel and downward travel of themask sheet 62, thereby varying the number of images displayed in eachrevolution of the cam 88. The RPM of the drive motor 84 can be varied toincrease or decrease the time cycle of the image changes and such changewill also result in longer or shorter dwell time on each image duringthe cycle.

The cam 88 dimension and the short roller 64, 66 dimensions, however,could also be varied to achieve similar results.

The cam 88 may be a fixed velocity cam or a constant rise and quickreturn cam depending on story line or animation image exposure.

The display, therefore, can be a variable time image effect, a staticdisplay or a display in animation mode.

Assuming a cam lift of 20 mm, an overall distance of 127.5 mm between apivot point 99 and the linkage mechanism 96 (B) and a distance of 85 mmbetween the pivot point 99 and the cam follower lever (A), the maximumoscillatory movement is 30 mm. This is calculated by:${{Cam}\quad {lift}\quad \times \frac{B}{A}} = C$

Thus, the incorporation of a cam follower lever confers a 50% mechanicaladvantage in observed oscillatory movement over the actual cam 88 lift.The actual mechanical advantage observed will depend on the B:A ratioand can be varied as desired.

Assuming a drive roller radius of 15 mm (E) and a lever length of 50 mm(D), the maximum oscillatory movement conveyed to the one of the masksheet or image sheet being moved is 9 mm. This is calculated as follows:$\frac{C \times E}{D} = F$

Thus, assuming an image pitch (width) of 1.5 mm, six sequential seriesof strip images would be visible per cam lift and, therefore, twelveseries of strip images are visible, in turn, per revolution of theconstant rise/constant fall cam 88.

When it is desired to provide twelve series of strip images to beviewed, in turn, per revolution of the cam 88, this can conveniently beachieved in the following manner, whilst maintaining distances A, D andE constant at, respectively, 85 mm, 50 mm and 15 mm and a constant camlift of 20 mm.

Image Device Pitch B C F Size (mm) (mm) (mm) (mm) A2 0.7 59.5 14 4.2 A10.85 72.25 17 5.1 A0 1.0 85 20 6.0 Six Sheet 1.5 127.5 30 9.0

Thus, in a preferred embodiment, the cam follower levers 90, 91 areprovided with a series of holes whose respective distances (B) and (C)from the pivot point 99 fulfil the above-mentioned guidelines for thesize of unit involved.

If the motor is a 0.625 rpm motor (⅝th), one complete rotation of thecam 88 will take 96 seconds and, if there are to be twelve pictures percomplete revolutions, the picture will change every eight seconds.

It will be appreciated that the same number of pictures per minute couldbe achieved by altering the cam lift dimension and/or the roller radius(E) and/or the cam follower lever dimension (A) and/or the leverdimension (D). Equally, the number of pictures per complete revolutioncan be varied by altering any of these factors.

The cam 88 is designed to be easily detached from the drive shaft 86,thereby permitting alteration of the cam lift dimension, which in turnalters the oscillatory travel of the mask sheet 62 within one revolutionof the drive shaft 86 and consequentially alters the number of imagechanges within the given time of one drive shaft 86 revolution.

For example, a constant velocity 88 cam may be replaced with a camhaving a constant velocity lift side and a quick return side. Such a cam88 is used for exposing images on the image sheet in animation whereby,when the cam follower levers 90, 91 are in contact with the cam 88 onthe lift side, images so placed on the image sheet will be exposed, bythe movement of the mask sheet 62, in animation and, as the cam followerlevers 90, 91 are in contact with the cam 88 on the quick return side,the mask sheet 62 is quickly returned to the start position to re-startthe animation sequence. In such an animated embodiment, the number ofdifferent image strips will equal the number of images displaced by thelift side of the cam 88.

It will also be appreciated that the illuminated display device 10 maybe provided with a single cam follower lever/linkage mechanism connectedto a single drive shaft and, in that event, the other shaft operates asa driven shaft (not shown). Such an arrangement is more suitable forsmaller, for example, A3 size, display devices. Any other method ofeffecting oscillating movement of the, or each, shaft is alsocontemplated by the present invention.

Adjustable first and second crank levers in the form of screws 92, 94extend diametrically through screw-threaded apertures provided in therespective first and second roller means 64, 66. The free end of eachcrank lever 92, 94 is connected by a respective linkage mechanism 96, 98to a respective cam follower lever 91, 90.

It will be appreciated that such adjustable crank levers 92, 94 permitadjustment of the distance between the mid point 65 of the first andsecond roller shafts 64, 66 and the point of connection to therespective linkage mechanisms 96, 98, whilst the radius of each rollershaft 64, 66 remains constant—thus, a mechanical advantage is gained.The mechanical advantage adds to the smoothness of movement of the masksheet 62.

The mechanical advantage is adjustable by moving each linkage mechanism96, 98 towards, or away from, the centre point 65 of the respectiveroller shafts 64, 66. This adjustment alters the length of movement ofthe mask sheet 62 and ensures a clear image at the top and bottom(change over points) of the rotating cam 88. An additional spring 79 isinterposed within one of the linkage mechanisms 96, 98 to impart theappropriate tension to the mask sheet 62. The tension of the spring 79is selected to provide the correct level of tension, and contact withthe image sheet 48 without undue friction being applied between theimage sheet 48 and the mask sheet 62, whilst also having sufficienttension so as to move the mask sheet 62 through the linkage mechanisms96, 98 as though it were a solid coupling.

Alternative means of oscillating the roller means 64, 66 (short driveshafts) have been tried but were unsuccessful in the clarity of imagedisplayed. For example, the short drive shafts could be drivenindividually by geared motors equipped to alternately reverse directionto provide an oscillating movement. Alternatively, the short driveshafts could be interconnected by chain or belt drive and driven by onegeared motor suitably equipped to give oscillating movement. Thedisadvantage of such drive systems is the loss of mechanical advantage,picture clarity adjustment at the reverse (change over) points and thedepth dimension of the display device necessary to contain suchmechanisms.

The motor 84 may be, for example, a micro gear motor with a rotationalspeed selected for the desired image display time. The distance ofmovement of the mask sheet 62 is controlled by the pitch dimension (camlift) of the cam 88 and the mechanical advantage of the first and secondcrank levers 92, 94. This mechanical advantage also reduces torque andnoise output of the motor 84.

The degree of oscillation of the mask sheet 62 is controlled by thecrank levers 92, 94 in the following manner. As the distance between thefree end of each crank lever 92, 94 and the respective longitudinalpivot axis of the first and second roller means 64, 66 is reduced, bypartially unscrewing the respective crank lever 92, 94 relative to itsroller means 64, 66, the crank lever's mechanical advantage or leveragedistance (“throw”) is reduced, which in turn reduces the degree ofoscillation of the mask sheet 62.

The illuminated display device 10 of the present invention is used inthe following manner. The desired image sheet 48 is located on theplaten 38 using the fixing means 50. The mask sheet 62 is then locatedover the image sheet 48, with its extensions 74, 74′ reversiblyconnected between the respective sleeves 70 and opposing roller means64, 66. The tensioning means 78 is then engaged. The mask sheet 62 isaligned with the image sheet 48 in the following manner. The image sheet48 is moved, after releasing the pin/nut/friction washer 60, so as toalign one series of image portions through the transparent strips 61 ofthe mask sheet 62. When the transparency sheet 48 is so aligned, thefixing means 50 are then tightened in place.

The front housing 14 is then fixed to the rear housing 12. When themoving means 82 of the illuminated display device 10 is actuated, thecontrolled oscillating movement of the drive shaft 68, under theinfluence of the moving means 82, in association with the tensioningmeans 78, permits sequential display of a series of images from theimage sheet 48.

The relationship between the multiple images on the image sheet 48 andthe transparent windows 61 on the mask sheet 62 are designed toaccomplish several important features in the illuminated advertisingdisplay unit 10 of the present invention. The multiple images, assembledas image portions in strip form on the image sheet 48, are varied, instrip form width, depending on the display unit dimensions. The width ofeach image strip 48 and the relationship with the transparent window 61width on the mask sheet 62 is vital to ensuring a satisfactory opticalquality and the desired visual display.

The relationship also permits a consistent optical quality when appliedthroughout the range of display unit sizes. Moving outside theboundaries described herein will make the unit unacceptable in opticalperformance. The image strip width has been formulated to comply withthe various display unit dimensions. This allows previous printingproblems associated with scaling up to larger display units to beovercome and, coupled with new printing techniques and materials used tocreate the image sheet 48 and the accompanying mask sheet 62, providesthe accuracy needed to provide the optical clarity required across thelength and breadth of each of the display units.

The control of stability of the image sheet 48 and the mask sheet 62under differing atmospheric conditions, for example, temperature andmoisture, is a further problem encountered on known display devices. Ithas been found that, where the image sheet 48 and mask sheet 62 aremanufactured by different printing techniques, the materials, or films,for both image sheet 48 and mask sheet 62 should have similar expansionor contraction properties under differing conditions. Preferably, thematerials of the respective image sheet 48 and the mask sheet 62 shouldhave minimal, most preferably no, expansion or contraction propertiesunder the usually encountered atmospheric conditions.

The accuracy of printing the multiplicity of image portions in stripform, and the co-operating transparent windows 61 on the mask sheet 62must be maintained over the overall length, to project a consistentoptical display over the entire surface of the display unit 10 as themask sheet 62 oscillates, thereby revealing image by image by image inturn.

Suitable printing techniques include, for example, ink jet, flat bed,laser or photographic imaging.

Limitations in printing technology have hitherto been the principlelimiting factors in previous designs whereas, under the presentinvention, for example, an image strip width could be 0.5 mm on an A3size and up to 2.4 mm on a six sheet size display unit. Table 1 showsthe preferred dimensions and limiting dimensions.

TABLE 1 Strip Image Width Transparent Window Width (mm) (% of preferredstrip Unit Pre- image width) Size Minimum Maximum ferred Minimum MaximumPreferred A2 0.4 1.2 0.8 30 60 45 A1 0.5 1.5 1.0 30 60 45 A0 0.6 1.8 1.230 60 45 6 0.8 2.4 1.6 30 60 45 sheet

Thus, the preferred transparent window widths 61 for a mask sheet 62 foruse of an A2, A1, A0 or six sheet unit size would be 0.36 mm, 0.45 mm,0.54 mm or 0.72 mm, respectively.

The mask sheet 62 has an arrangement of transparent windows 61 andopaque strips 63 (see FIG. 7). The transparent windows 61 display oneimage at a time while the opaque strips 63 obscure the other series ofimage portions in strip form on the image sheet 48.

A feature of the invention is the relationship between the image stripwidth and the width of the transparent window 61 on the mask sheet 62.

Assuming that an image sheet 48 contains three series of strip images,each of a preferred 0.8 mm width (A2 unit size), and assuming that themask sheet 62 has a preferred transparent window 61 of a preferred 0.36mm width (45% of strip width), this means that each opaque strip 63 hasa width of 3×0.8 mm-0.36 mm (or 2.04 mm).

For example, if the transparent window 61 on the mask sheet 62 is thesame width as the image strip width then the image will only bedisplayed momentarily as the mask sheet 62 moves upwards and downwardsduring oscillation. Such a changeover would show pictures overlappingfor 50% of the time. On the other hand, if the transparent window 61 ismuch narrower than the image strip width, then the light illuminationwill be restricted, the traverse time of the transparent window acrossthe image strip increased and the changeover time to the next picturetoo short having the effect of losing the attraction of movement.

It has been found, for best results, that the transparent windows 61 onthe mask sheet 62 should correspond to between 30% and 60% of the imagestrip width, preferably about 45% of the image strip width.

As previously described, the y-axis curvature of the platen 38 has beenchosen to minimise friction between the image sheet 48 and the masksheet 62 while maintaining constant overall contact between both. Anyloss of contact may result in part of another image being shown at thepoint where contact has been lost. The friction therefore between theimage sheet 48 and the mask sheet 62 can result in wear on eithertouching surface.

Such wear initially becomes evident as scratches. It is envisaged thatthe image sheet 48 will be changed frequently as advertising needschange, however the mask sheet 62 may remain in place for up to one yearor until the next normal maintenance programme. Friction is vastlyreduced by application of a dry lubricant, for example talcum powder.

In addition, applying a clear micro film laminate to either, or one of,the touching surfaces along with the dry lubricant greatly enhances thevisual performance for adverts used in the longer term.

It will be appreciated that, in the illustrated embodiment, the imagesheet 48 is stationary on the platen 38, whilst the mask sheet 62 isurged to oscillatingly move over the fixed image sheet 48. Equally, themask sheet 62 might be fixed in place and the image sheet 48 arranged tooscillatingly move relative to the mask sheet 62.

It will further be appreciated that, in the illustrated embodiment, themask sheet is located in touching contact and over the image sheet 48.Equally, this arrangement can be reversed as desired.

What is claimed is:
 1. An illuminated display device comprising anilluminated image sheet, comprising a plurality of series of imageportions; a mask sheet having alternate opaque and transparent strips,the mask sheet being located in face-to-face relation to the imagesheet; first and second roller means in a substantially parallelspaced-apart arrangement relative to the image sheet and the mask sheet,the first and second roller means being operatively associated with oneof the image sheet and the mask sheet; and means to oscillatingly movethe one of the image sheet and the mask sheet relative to the other ofthe image sheet and the mask sheet, the moving means including a drivemeans; a cam rotatably driven by the drive means; a cam follower leverassociated with the cam; and a crank mechanism comprising a crank leveroperatively associated with the first roller means and a linkagemechanism connecting the cam follower lever and the crank lever.
 2. Anilluminated display device according to claim 1, in which the imagesheet comprises at least three series of image portions.
 3. Anilluminated display device according to claim 1, in which two opposingcam followers and two opposing crank mechanisms are provided so that thedrive means is arranged, in operative association with the first andsecond roller means, to impart oscillating movement to the first rollermeans and equal and opposite oscillating movement to the second rollermeans.
 4. An illuminated display device according to claim 1, in whichthe length of the first and second roller means is 10%-50% of the widthof the image sheet.
 5. An illuminated display device according to claim1, in which the one of the image sheet and the mask sheet which isoperatively associated with the first and second roller means istensioned by providing at least one pair of tension springs, the, oreach, pair of tension springs forming a substantially V-shapedarrangement of tension lines, the apex of the substantially V-shapedarrangement being the transverse mid-line of the opposite roller means;and an opposing at least one pair of tension springs forming asubstantially inverted V-shaped arrangement of tension lines, thesubstantially inverted V-shaped arrangement apex being the transversemid-line of the opposite of the roller means.
 6. An illuminated displaydevice according to claim 1, in which the image sheet and the mask sheetare supported on a platen and the maximum height of curvature of theplaten in the y-axis is between 0.3 and 2% of the length of the platenin the y-axis.
 7. An illuminated display device according to claim 6, inwhich the one of the image sheet and the mask sheet which is operativelyassociated with the first and second roller means is tensioned byproviding at least one pair of tension springs, and in which the atleast one pair of tension springs are arranged below a notionalextension of the y-axis curvature of the platen.
 8. An illuminateddisplay device according to claim 6, in which the platen has a maximumtransverse curvature of between 3% and 20% of the maximum longitudinalcurvature of the platen.
 9. An illuminated display device according toclaim 1, in which each image portion forming one series of imageportions has a pitch of 0.025-0.25% of the y-axis length of the imagesheet.
 10. An illuminated display device according to claim 9, in whicheach transparent window of the mask sheet has a pitch of 30-60% of thepitch of each image portion.
 11. An illuminated display device accordingto claim 1, in which the image sheet comprises at least four series ofimage portions.
 12. An illuminated display device according to claim 1,in which the image sheet comprises five series of image portions.
 13. Anilluminated display device according to claim 1, in which the imagesheet and the mask sheet are supported on a platen and the maximumheight of curvature of the platen in the y-axis is 0.8% of the length ofthe platen in the y-axis.
 14. An illuminated display device according toclaim 1, in which each image portion forming one series of imageportions has a pitch of 0.05-0.21% of the y-axis length of the imagesheet.
 15. An illuminated display device according to claim 1, in whicheach image portion forming one series of image portions has a pitch of0.075-0.15% of the y-axis length of the image sheet.
 16. An illuminateddisplay device according to claim 9, in which each transparent window ofthe mask sheet has a pitch of about 45% of the pitch of each imageportion.
 17. An illuminated display device according to claim 14, inwhich each transparent window of the mask sheet has a pitch of about 45%of the pitch of each image portion.
 18. An illuminated display deviceaccording to claim 15, in which each transparent window of the masksheet has a pitch of 30-60% of the pitch of each image portion.
 19. Anilluminated display device according to claim 15, in which eachtransparent window of the mask sheet has a pitch of about 45% of thepitch of catch image portion.
 20. An illuminated display deviceaccording to claim 13, in which the one of the image sheet and the masksheet which is operatively associated with the first and second rollermeans is tensioned by providing at least one pair of tension springs,and in which the at least one pair of tension springs are arranged belowa notional extension of the y-axis curvature of the platen.